15.在△ABC中,内角A,B,C所对的边分别为a,b,c,若a2+b2=2a+6b-10,且c2=a2+b2+ab,则△ABC的面积为( )
| A. | $\frac{\sqrt{3}}{2}$ | B. | $\frac{3\sqrt{3}}{3}$ | C. | $\frac{\sqrt{3}}{4}$ | D. | $\frac{3\sqrt{3}}{4}$ |
14.锐角△ABC中,a,b,c分别是角A,B,C的对边,若B=2A,则$\frac{b}{a}$的取值范围是( )
| A. | (0,2) | B. | ($\sqrt{2}$,2) | C. | ($\sqrt{2}$,$\sqrt{3}$) | D. | ($\sqrt{3}$,2) |
9.已知0<x<8,则x(8-x)的最大值是( )
0 226513 226521 226527 226531 226537 226539 226543 226549 226551 226557 226563 226567 226569 226573 226579 226581 226587 226591 226593 226597 226599 226603 226605 226607 226608 226609 226611 226612 226613 226615 226617 226621 226623 226627 226629 226633 226639 226641 226647 226651 226653 226657 226663 226669 226671 226677 226681 226683 226689 226693 226699 226707 266669
| A. | 7 | B. | 12 | C. | 15 | D. | 16 |